A stent refers to a tubular medical tool that is placed in a stenosed portion or the like for dilating the stenosed portion, etc., to secure a necessary lumen region when a blood vessel or a lumen in an organism is stenosed or occluded. The stent is inserted into a body with its diameter kept small, and is expanded in a stenosed portion, etc., to have a larger diameter so that the above lumen is dilated and sustained.
Conventional stents are typically as shown in FIGS. 11 and 12. However, these have had the following drawbacks. FIG. 11A and FIG. 12A show stents before expansion, and FIG. 11B and FIG. 12B show the stents after expansion.
In a stent 201 shown in FIG. 11, cells 206 constituting a ring unit 204 have a structure in which three linear portions 207 are connected in parallel and a curved portion 206A between the cells 206 is arranged so as to face a space 206B in the vicinity of cells 206 constituting another ring unit 204. Having the above structure, the above stent is excellent in proper radial sustaining force (which, in a general expression, means a force to sustain an expansion state of the stent against an external force from and through a blood vessel wall when the stent is expanded to be fixed to the vessel wall) and flexibility. Since, however, the stent is inserted through tortuous parts of a blood vessel, along the curves of it, during expansion or delivery, the cells 206 partly project outward to be caught by the wall of the vessel, so that the delivery has been sometimes difficult (which will be referred to as “flare phenomenon” hereinafter).
In a stent 241 shown in FIG. 12, cells 246 which constitute a ring unit have a structure in which generally-<-shaped struts (linear bodies) 247 are connected with a connector portion 245. Therefore, the stent 241 has advantages that it has a strong radial-sustaining force and that the above generally-<-shaped struts 247 are not warped outward during expansion or insertion through a tortuous blood vessel. However, the defect with it is that it lacks flexibility. It is considered that the above problem is caused since each connector portion 245 has only one curved portion and also since the connector portion 245 is of small length.
The conventional stents thus have the problem that they are not well-balanced in flexibility and radial sustaining force.
The present inventors have made diligent studies for overcoming the above problems in order to provide a new stent having both flexibility and radial sustaining force, and have arrived at the present invention.